1. Field of the Invention
The present invention relates to a thin spindle motor and a hard disk drive therewith.
2. Description of Related Art
In general, 2.5-inch hard disk drives mounted in notebook computers normally have a thickness of 9.5 mm. Recently, however, thinner hard disk drives with thicknesses of not more than 7 mm have been used in slim notebook computers. Thus, spindle motors for such hard disk drives are also required to be thinner than usual. In addition, notebook computers are also required to consume less electricity.
A stator core of a standard spindle motor has a structure such that stator laminations having teeth portions are formed by press cutting a magnetic steel sheet with a thickness of 0.35 mm, and then a number of stator laminations are laminated and fixed by swaging. If a stator core using the stator laminations with a thickness of 0.35 mm is made thinner than a conventional level, the number of the stator laminations decreases resulting in an increase of the magnetic loss. Thus, it is difficult to reduce both the thickness of the stator core and the power consumption.
Japanese Unexamined Patent Application Laid-Open No. 2002-171701 discloses a technique for forming a core of a spindle motor with a particular thickness by laminating thinnest possible magnetic steel sheets in order to decrease the magnetic loss and the power consumption. It is also disclosed that the core preferably has a structure such that one side of the magnetic steel sheet is recessed so as to project to the other side in order to provide a swaging portion formed of a set of the recess and the projection, and a plurality of the magnetic steel sheets is laminated by swaging the swaging portions.
Japanese Unexamined Patent Application Laid-Open No. 11-113195 discloses a structure of an armature core of a revolving-field type generator. The armature core has teeth portions that are located radially from a shaft center and formed by providing protrusions at an inner circumference thereof. A swaging portion is press cut into a V shape or a trapezoidal shape in the vicinity of a top end portion of each of the teeth portions. In order to provide a laminated structure of plural armature core sheets D1 to Dn, the laminated armature core sheets D1 to Dn are securely engaged with each other by fitting the swaging portions.